(CW) for wastewater treatment in middle- and high-latitude regions with cold 

 climates. Specific goals of the study are to: (a) provide additional information on 

 the feasibility of using sub-surface flow (SSF) wetlands to treat wastewater in 

 cold climates, (b) develop objective design and operational criteria for constructed 

 SSF wetlands based on evaluation and modeling of key process controls, (c) 

 document the quality of water emerging from model SSF wetlands. 



The aim of this paper is to present priority parameters as a time series which 

 can be compared to various operational changes and plant life cycle changes for 

 three different plant treatments. Priority parameters routinely sampled (once per 

 residence time in) in both influent and effluent include: COD as a measure of total 

 organics, the nitrogen species NH 4 , NO3, NO2, phosphate PO4, and sulfate S0 4 . 

 Continuously monitored parameters include temperature (since project initiation) 

 and effluent flow rate (recently). Other water quality parameters including total 

 Kjeldahl nitrogen (TKN) and pH are less frequently sampled. 



Methods 



Eight constructed wetlands (CW cells) were constructed and placed in an 

 environmentally controlled greenhouse. Each CW cell is 152 cm long, 76 cm 

 wide, and 53 cm deep and filled with gravel (19 mm > size > 13 mm) to a depth 

 of 46 cm. The average initial porosity was 0.40. Water temperature at a depth of 

 36 cm was measured in each cell by a differential thermocouple which records 

 data every half hour. Greenhouse air temperature was also measured at the same 

 frequency. Additional details are found in Biederman and Stein (1997). 



Three cells each were planted with Typha sp. (broad-leaf cattail) and Scirpus 

 sp. (hard-stem bulrush) on December 5, 1995, while two cells remained implanted 

 as treatment controls. The plants were recovered from a native wetland near 

 Bozeman, MT. Root stocks were planted on 30-cm centers at a depth of 7 cm. 

 Both species exhibited nearly 100% transplant success and rapid initial growth. 

 At approximately nine months after planting, stable heights of 1 m for the bulrush 

 and 2 m for the cattail were achieved. At this time, depth of root penetration 

 below the gravel surface was 27 cm for the cattail and 46 cm (to cell bottom) for 

 the bulrush. However, root density decreased as a function of depth for both 

 species. Basal density of the cattails appeared to have stabilized at approximately 

 one stalk per 10 cm over the entire wetland surface, while bulrush density was 

 more varied, as the original transplant plugs could still be distinguished after nine 

 months. Both plant species were observed to enter a period of relative dormancy 

 from December 1996 through May 1997, after which time vigorous regrowth 

 began. Within a period of one month, both species achieved heights of 2 to 3 m 

 and very dense basal coverage of their entire respective wetland cells. In early 

 October 1997 the plants once again entered a period of relative dormancy. 



A continuous flow of synthetic wastewater has been delivered by a 

 peristaltic pump system at a rate of 30 ml/min/cell ±5% (t H = 5 days) since April 

 5, 1996. Sampling of influent and effluent every fifth day (once per t H ) has 

 occurred continuously since June 1996. All samples are analyzed for 

 concentrations of nitrate, phosphate and sulfate by ion chromatography. 



Stem et al 



